OLED, as a new type of display technology, has unique advantages such as self-illumination, wide viewing angle, low power consumption, high efficiency, thin, rich colors, fast response, extensive application temperature range, low driving voltage, applicable for flexible and transparent display panel, and environmental friendliness, etc. Therefore, OLED technology can be applied to flat panel displays and new generation of lighting, or can be used as backlight of LCD. In 1987, Kodak (Tang et al) firstly made a sandwiched bilayer devices using 8-hydroxyquinoline aluminum (Alq3) as the light emitting layer and a triphenylamine derivative as the hole transporting layer through thin-film vacuum evaporation technique. The device achieved a luminance up to 1000 cd/m2 at a driving voltage of 10 V (Tang C. W., Vanslyke S. A. Appl. Phys. Lett. 1987, 51, 913-916). This technological breakthrough had aroused widespread notice in the scientific community and industry, and since then the research and applications of organic light-emitting technology become a hot issue. Subsequently, in 1989, with the invention of host-guest emission technology, the luminous efficiency and lifetime of OLED had been greatly improved. In 1998, Forrest et al found the electrophosphorescence, which lifted the theoretical limit of organic electroluminescent quantum efficiency from 25% to 100% (Baldo M. A., Forrest S. R. Et al, Nature, 1998, 395, 151-154), bringing the research of organic light-emitting technology into a new era with extended field of research.
A classic three-layer OLED comprises a hole transport layer, a light emitting layer and an electron transport layer. adopts traditional electron transport material is Alq3, which has good film-forming propertiy and thermal stability, but its strong green emission and low electron mobility restricts its industrial applications. Subsequently, some electron transport materials with excellent performance, such as TPBI, BCP, Bphen, are also widely used in the OLED. The existing material of light-emitting layer can be divided into two categories, namely, fluorescent material and phosphorescent material, which are often adopted in guest-host doping technology.
CBP (4,4′-bis(9-carbazolyl)-biphenyl) is a highly efficient and high-triplet-energy phosphorescent host material. When CBP is used as the host material, triplet energy can be smoothly transferred to phosphorescent material, producing efficient red and green emission. However, such representative host materials are restricted to use because of their poor thermal stability and short lifetime of manufactured devices.
Although OLED has made considerable progress after 20 years of development, and organic materials have also been in constant development, there are still very few materials that can meet the market demands with good device efficiency and lifetime to give excellent performance and stability at the same time.
Fluoranthene, as an electroluminescent material, is widely used as electron transport material, hole transport material and light-emitting material. However, according to the known reports, either the performances of devices are not described in details, or the devices only had low efficiency or poor stability. In the present invention, a series of new compounds based on fluoranthene are disclosed and used in OLEDs.